Search

Production of inoculum of Colletotrichum acutatum from both previously infected and overwintered tissue, as well as newly developed plant tissue of sour cherry (Prunus cerasus), was studied in southern Norway. Plant parts were sampled from commercial, private, or research orchards, and incubated for 2 to 14 days (time depended on tissue type) in saturated air at 20°C. In early spring, abundant sporulation was found on scales of overwintered buds and shoots. A mean of 35% infected buds in four cultivars was observed, with a maximum of 72% of the buds infected in one of the samples. Over 3 years, the seasonal production of overwintered fruit and peduncles of cv. Fanal infected the previous year was investigated. In all three years, the infected plant material was placed in the trees throughout the winter and the following growing season; in two of the years, fruit and peduncles were also placed on the ground in the autumn or the following spring. Old fruit and peduncles formed conidia throughout the season, with a peak in May and June. Spore numbers declined over the season, but the decline was more rapid for plant material on the ground than in the trees. On average over 2 years, 68.7, 24.0, or 7.3% of the inoculum came from fruit placed in the trees, placed on the ground in spring, or placed on the ground the preceding autumn, respectively. The number of fruit and peduncles attached to the trees in a planting of cv. Hardangerkirsebær was followed from February to July one year, and although there was a decline over time, fruit and/or their peduncles were still attached in substantial numbers in July, thus illustrating their potential as sources of inoculum. In observations over 2 years in a heavily infected orchard of cv. Stevnsbær, 75 and 47% of flowers and newly emerged fruit, respectively, were infected. Artificially inoculated flowers and fruit produced conidia until harvest, with a peak in mid-July. It may be concluded that previously infected and overwintered, as well as newly emerged tissue of sour cherry, may serve as sources of inoculum of C. acutatum throughout the growing season. [ABSTRACT FROM AUTHOR]

It is demonstrated that closely related viruses within the family Betaflexiviridae are associated with a number of diseases that affect sweet cherry (Prunus avium) and other Prunus spp. Cherry rusty mottle- associated virus (CRMaV) is correlated with the appearance of cherry rusty mottle disease (CRMD), and Cherry twisted leaf-associated virus (CTLaV) is linked to cherry twisted leaf disease (CTLD) and apricot ringpox disease (ARPD). Comprehensive analysis of previously reported full genomic sequences plus those determined in this study representing isolates of CTLaV, CRMaV, Cherry green ring mottle virus, and Cherry necrotic rusty mottle virus revealed segregation of sequences into four clades corresponding to distinct virus species. High-throughput sequencing of RNA from representative source trees for CRMD, CTLD, and ARPD did not reveal additional unique virus sequences that might be associated with these diseases, thereby further substantiating the association of CRMaV and CTLaV with CRMD and CTLD or ARPD, respectively. Based on comparison of the nucleotide and amino acid sequence identity values, phylogenetic relationships with other triple-gene block- coding viruses within the family Betaflexiviridae, genome organization, and natural host range, a new genus (Robigovirus) is suggested. [ABSTRACT FROM AUTHOR]

Little cherry disease, one of the major viral diseases of sweet cherry (Prunus avium) worldwide, is associated with either of two closteroviruses, Little cherry virus 1 (LChV- 1) and Little cherry virus 2 (LChV-2). Two sets of primers corresponding to a portion of the replicase gene of LChV-1 and LChV-2 were used in one-tube reverse-transcription polymerase chain reactions to detect these viruses in total RNA extracts of field-collected sweet cherry tissues. LChV-1 and LChV-2 were detected both alone and in combination in five sweet cherry orchards in Washington State. Sequence analysis of a 240-nucleotide (nt) fragment of the replicase open reading frame (ORF) lb and a 232-nt fragment from a portion of ORF8 and the 3′ untranslated region (UTR) of LChV-1 indicated that North American (NA) isolates shared 90 to 99% nucleotide identity in both genome segments analyzed. In contrast, comparisons of NA isolates to two Eurasian isolates of LChV-1 indicated shared nucleotide identities of 79 to 82% in the replicase fragment and 89 to 90% in the ORF8/3′UTR fragment. Sequence variation in the replicase region did not affect detection of LChV-1 in 12 isolates using the replicase-specific primers reported here. This article represents the first report of LChV-1 and LChV-2 in sweet cherry in Washington. [ABSTRACT FROM AUTHOR]

The intensive use of site-specific fungicides in agricultural production provides a potent selective mechanism for increasing the frequency of fungicide-resistant isolates in pathogen populations. Practical resistance occurs when the frequency and levels of resistance are great enough to limit the effectiveness of disease control in the field. Cherry leaf spot (CLS), caused by the fungus BIumeriella jaapii, is a major disease of cherry trees in the Great Lakes region. The site-specific sterol demethylation inhibitor fungicides (DMIs) have been used extensively in the region. In 2002, CLS control failed in a Michigan orchard that had used the DMI fenbuconazole exclusively for 8 years. That control failure and our observations from around the state suggested that practical resistance had developed in B. jaapii. Field trial data covering 1989 to 2005 for the DMIs fenbuconazole and tebuconazole supported observations of reduced efficacy of DMIs for controlling CLS. To verify the occurrence of fungicide-resistant B. jaapii, monoconidial isolates were collected in two surveys and tested using a fungicide-amended medium. In one survey, 137 isolates from sites with different DMI historics (no known history, mixed or alternated with other fungicides, and exclusive use) were tested against 12 concentrations of fenbuconazole, tebuconazole, myclobutanil, and fenarimol. Isolates from sites with no prior DMI use were DMI sensitive (DMIS = no colony growth at 0.2 µg/mI a.i.) whereas the isolates from the site with prior exclusive use showed growth at DMI concentrations 3 to >100 times higher, and were rated as DMI resistant (DMIR). A second survey examined 1,530 monoconidial isolates, including 1,143 from 62 orchard Sites in Michigan, where DMIs had been used to control CLS. Resistance to fenbuconazole was detected in 99.7% of the orchard isolates. All isolates from wild cherry trees were sensitive and isolates from feral and dooryard trees showed a range of sensitivities. A polymerase chain reaction (PCR)-based detection method for identifying B. jaapii and DMIR was developed and tested. The species-specific primer pair (Bj-F and Bj-R) based on introns in the CYP51 gene of B. jaapii, and the DMIR-specific primer pair (DMI-R-Bj-F and DMI-R-Bj-R) based on an insert found upstream of CYP51 in all DMIR isolates, provided an accurate and rapid method for detecting DMIR B. jaapii. The PCR-based identification method will facilitate timely decision making and continued monitoring of DMIR subpopulations in response to management programs. [ABSTRACT FROM AUTHOR]

Several abstracts of the articles related to plant pathology are presented, including "Wilt and Collapse of Cuphea ignea Caused by Phytophthora tropicalis in Italy," "Tissue Necrosis of Sour Cherry Fruits: An Unusual Disease Occurrence Caused by a Phoma sp. in Serbia," "First Report of Alternaria Leaf Spot on Cherry Trees in Greece," "New Outbreaks of Bacterial Wilt of Dry Bean in Nebraska Observed From Field Infections," and "Occurrence of Citrus Leprosis Virus in Llanos, Colombia."

Demand for organically grown fruit, including sour cherry, is rising in Europe and the United States, but the limited tools for disease management have not been thoroughly investigated. In this study, management of brown rot blossom blight, caused by Monilinia laxa, was examined for organic sour cherry production in Hungary. Combinations of sanitation practices and fungicide treatments, including copper hydroxide, lime sulfur, and micronized and nonmicronized wettable sulfur, were investigated in 2 years and two cultivars. The effect of fungicide treatments on yield and phytotoxicity on spur-leaf clusters was also determined. Among fungicide treatments suitable for organic production, copper hydroxide and lime sulfur alone or in combination with micronized wettable sulfur were most effective for blossom blight control when applied twice (at closed blossom and full bloom) or three times (at closed blossom, full bloom, and petal fall) during bloom. Both treatments were not as effective as the conventional standard and caused more damage on spur-leaf clusters during wet weather conditions, but significantly increased crop yield compared with the untreated control or wettable sulfur treatments. Micronized and nonmicronized sulfur applied up to three times during bloom were equally effective, did not impact yield, were not phytotoxic, and reduced blossom blight compared with the untreated control. Sanitation (the removal of blighted twigs and mummified fruit) reduced blossom blight in both cultivars compared with nonsanitized plots when disease pressure was high. The need for an integrated approach to effectively manage blossom blight in organic sour cherry production is discussed. This is the first in-depth characterization of cultural and chemical brown rot blossom blight control options for organic sour cherry production. [ABSTRACT FROM AUTHOR]

The LC5 isolate of Little cherry virus (LChV-LC5) is one of at least two distinct viruses contributing to a severe disease of cherry (Little cherry disease [LChD]) in British Columbia. A near-complete nucleotide sequence of LChV-LC5 is available as well as polyclonal antibodies against LChV-LC5 coat protein produced in bacterial cells. A survey for LChV-LC5—infected trees in the Okanagan Valley and Kootenay region of British Columbia was carried out using enzyme-linked immunosorbent assays (ELISA) and LChV-LC5 antibodies. Reverse transcriptase polymerase chain reaction (RT-PCR) and sequence analysis of four different regions of the genomes of 31 of these isolates have been conducted. A high level of sequence variability was found: nucleotide sequence divergence between LChV-LC5 and the other sequenced isolates ranged from 0 to 19.7%, and amino acid sequence divergence ranged from 0 to 9.1%. Further examination of RT-PCR and sequence data identified six discrete groups of isolates, including a group identical to LChV-LC5. The high level of divergence in LChV-LC5 isolates occurring in British Columbia suggests that caution should be used in the selection of methods used for diagnosis during surveys for this virus. [ABSTRACT FROM AUTHOR]

The article discusses the plum bark necrosis stem pilting and cherry virus An is associated with virus in cherry in Chile including collecting of samples, RNA extraction and high-throughput sequencing.

The article discusses report of Cherry mottle leaf virus infecting cherry in China which mentions disease symptoms including puckering of leaves, by researchers including J. J. Li from Department of Plant Pathology, College of Plant Protection, Shandong Agricultural University in Shandong, China.

An abstract of the article "First Report of Little cherry virus 2 in Flowering and Sweet Cherry trees in China," by W. L. Rao and colleagues is presented.

An abstract of the article "First Report of Leaf Spot Caused by Pseudocercospora pruni-persicicola on Sweet Cherry in Korea" by I.Y. Choi is presented.

An abstract of the article "First Report of Aspergillus niger Causing Postharvest Fruit Rot of Cherry in the Prefectures of Imathia and Pella, Northern Greece," by T. Thomidis and E. Exadaktylou is presented.

An abstract of the article "First Report of Cherry green ring mottle virus on Cherry and Peach Grown in China," by J. F. Zhou and G. P. Wang is presented.

An abstract of the article "First Report of Stem Canker on Cherry Caused by Phomopsis perniciosa in Shandong Peninsula, Eastern China," by C. X. Wang and colleagues is presented.

An abstract of the article "Characterization of Cherry leafroll virus in Sweet Cherry in Washington State," by K. C. Eastwell and W. E. Howell is presented.

The article describes the first reported case of Cherry virus A (CVA) in sweet cherry in China. It relates that mottling and mosaic symptoms were observed in two trees with CVA infection, which was confirmed by reverse transcription polymerase chain reaction (RT-PCR). It is noted that the analysis of the predicted amino acid sequence of the 873-bp fragments showed that it is 98% identical with the type isolate of CVA from Germany.

The article presents a plant disease research on root and collar rot by "Phytophthora cryptogea" on sweet cherry in Italy. Decline symptoms of "Prunus avium" grafted on wild rootstocks of "Prunus avium" consisted of reduced tree vigor, yellowing of leaves, and development of root and collar rot. A reddish brown discoloration of the inner bark and wood was observed on symptomatic trees in which symptoms were recorded in three cherry orchards seasonally submitted to soil saturation conditions. It is found out that the presence of "P. cryptogea" in cherry orchards is of significant concern because of its aggressiveness to this host and woody hosts.